free-bored

[free-bawrd, -bohrd] /ˈfriˈbɔrd, -ˈboʊrd/

adjective

1.

(of a rifle) having a bore that is not rifled within a short distance of the breech, so that a fired cartridge travels about 1/2 inch (1.3 cm) before being engaged by the lands, thus reducing initial high pressures.